The subject matter disclosed herein relates to imaging and, more particularly, to apparatus and methods for processing analog signals generated by solid state photomultiplier devices.
A silicon photomultiplier (SiPM) is an array of passively quenched Geiger-mode avalanche photodiodes (APD) for detecting impinging photons. SiPM can provide information about certain parameters, such as the time of the impingement event, the energy associated with the event, and the position of the event within the detector. These parameters can be determined through processing algorithms applied to the analog signals generated by the SiPM. Some conventional SiPMs can produce very fast signals, which provides a high degree of timing accuracy.
SiPMs provide certain advantages over conventional vacuum photomultiplier tubes (PMTs), and are therefore being used in many applications, including positron emission tomography (PET) for medical imaging. These advantages include better photon detection efficiency (i.e., a high probability of detecting an impinging photon), compactness, ruggedness, low operational voltage, insensitivity to magnetic fields and low cost. However, due to its small size of 2 mm×2 mm to 6 mm×6 mm, compared to a PMT in the dimension of 38 mm×38 mm, multiple SiPMs are required to cover the area of the PMT, which demands an increased amount of readout electronics. In order to take advantage of the improvement in SiPMs without a large cost in both cost and power consumption in the readout electronics, there is a need to simplify the readout architecture coupled to the SiPMs while keeping the integrity of SiPM signals in both rising edge and signal length.